Secondary battery with enhanced ability to prevent leakage

ABSTRACT

A secondary battery includes a can having an interior space, an electrode assembly provided in the interior space of the can, and a cap assembly seated on an opening formed in the can to seal the can and electrically connected to the electrode assembly. The cap assembly includes a cap plate connected to the opening to seal the can; a tab plate mounted to one side of the cap plate and connected to the electrode assembly; an insulating plate interposed between the cap plate and the tab plate; an electrode pin passing through the cap plate, the tab plate, and the insulating plate to interconnect these elements; and an insulating gasket interposed between the cap plate and the electrode pin. Also, the electrode pin includes a head portion mounted to one side of the cap plate and formed in multiple stages in an area contacting the insulating gasket; and a column extending from the head portion and passing through the insulating gasket, the cap plate, the insulating plate, and the cap plate.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from applications for CAP ASSEMBLY AND SECONDARY BATTERY THEREWITH earlier filed in the Korean Industrial Property Office on 15 Apr. 2002 and there duly assigned Serial No. 2002-20402, and for SECONDARY BATTERY WITH ENHANCED PREVENTING CHARACTERISTIC FOR LIQUID LEAKAGE earlier filed in the Korean Industrial Property Office on the 15 Oct. 2002 and there duly assigned Serial No. 2002-62901.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a secondary battery, and more particularly, to a cap assembly for a secondary battery.

2. Description of the Related Art

A secondary battery may be recharged for repeated use. Secondary batteries may be made to small sizes and large capacities, and are cylindrical, prismatic, button-shaped, etc. depending on an external shape of a case, which holds an electrode assembly (i.e., pole plate assembly).

The prismatic battery will be used as an example to describe a structure of the conventional secondary battery. The basic structure of the conventional prismatic secondary battery includes a prismatic can; an electrode assembly formed in a jelly roll configuration by interposing separators between anode plates and cathode plates, on which an active material is deposited, the electrode assembly being provided in the can; and a cap assembly provided to an opening of the can to seal the same, the cap assembly being electrically connected to the electrode assembly.

The cap assembly includes a cap plate integrally assembled to the can to form a seal with the same; a tab welding plate for fixing an electrode tab that is connected to one of the electrode plates of the electrode assembly (e.g., one of the cathode plates); an insulating member provided as insulation between the cap plate and the tab welding plate; an electrode pin that passes through holes formed in the cap plate, the tab welding plate, and the insulating member to contact the tab welding plate for electrical connection to the same; and a gasket providing insulation between the electrode pin and the cap plate.

However, with the use of the cap plate having the structure described above by the secondary battery, in the case where the gasket experiences problems such that it undergoes deformation, electrolyte within the can easily leaks such that battery performance is reduced. This is a result of an area between the electrode pin and the gasket that is closely contacted, that is, a connecting area of a head portion and a column of the electrode pin being smooth and flat such that if the gasket is deformed, the electrolyte within the can travels along the column of the electrode pin and easily exits the can through the head portion.

Further, a bottom surface of the insulating member that sits on the tab welding plate is flat such that during assembly of the cap assembly, when calking of the electrode pin to the cap plate, the insulating member, and the tab welding plate is performed, the force used during calking is applied to all of the insulating member such that a significant reactive force is generated from the insulating member. This reactive force acts to deform the insulating member itself such that the seal formed at the bottom of the cap assembly is broken or made less effective.

Finally, in the secondary battery having the cap assembly as described above, it is necessary to provide a separate space for the placement of the electrode tab between the tab welding plate and the electrode assembly. This interferes with attempts to maximize the volume of the electrode assembly within the can, which, in turn, makes increasing battery capacity difficult.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide a secondary battery that delays a leakage time in the case where leakage of electrolyte occurs to thereby prevent a reduction in the life span of the battery caused by electrolyte leakage.

It is another object of the present invention to provide a secondary battery that minimizes deformation of an insulating member during manufacture of the secondary battery (i.e., during calking of an electrode pin). As a result, a seal between a cap assembly and the remainder of the battery is improved.

It is still another object of the present invention to provide a secondary battery that reduces a space needed for a lead provided between a tab plate and an electrode assembly to allow for an increase in a volume of the electrode assembly.

In order to accomplish the above and other objects, accordingly in one embodiment, the present invention provides a secondary battery including a can having an interior space; an electrode assembly provided in the interior space of the can; and a cap assembly seated on an opening formed in the can to seal the can and electrically connected to the electrode assembly.

The cap assembly includes a cap plate connected to the opening to seal the can; a tab plate mounted to one side of the cap plate and connected to the electrode assembly; an insulating plate interposed between the cap plate and the tab plate; an electrode pin passing through the cap plate, the tab plate, and the insulating plate to interconnect these elements; and an insulating gasket to interposed between the cap plate and the electrode pin.

Further, the electrode pin includes a head portion mounted to one side of the cap plate and formed in multiple stages in an area contacting the insulating gasket; and a column extending from the head portion and passing through the insulating gasket, the cap plate, the insulating plate, and the cap plate.

The multiple stages of the head portion of the electrode pin are realized such that a center area of the head portion is formed protruding from a remainder of the head portion. Preferably, the multiple stage configuration of the head portion of the electrode pin includes a first stage having a predetermined thickness, and a second stage having a thickness that is less than the thickness of the first stage.

A surface of the second stage is uneven, and the second stage is formed having a thickness that increasingly expands in a direction away from a center of the second stage.

Further, a receiving area is formed in a surface of the tab plate facing the electrode assembly, and a lead is bent and mounted in the receiving area in a state electrically connected to the electrode assembly. The receiving area is formed as a groove in the tab plate.

The insulating plate has a hole through which the electrode pin passes, and a seal enhancing member is formed in a periphery of this hole to prevent deformation of the insulating plate during calking of the electrode pin.

The seal enhancing member is realized through a hilly spot formation that protrudes from one surface of the insulating plate around a periphery of the hole of the insulating plate.

The tab plate is made of a nickel alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

FIG. 1 is a partial sectional view of a secondary battery according to a preferred embodiment of the present invention;

FIG. 2 is a perspective view of an electrode pin of a cap assembly according to a preferred embodiment of the present invention;

FIG. 3 is a sectional view of a cap assembly according to a preferred embodiment of the present invention;

FIG. 4 is a sectional view of an insulating plate of a cap assembly according to a preferred embodiment of the present invention;

FIG. 5 is a cutaway perspective view of a conventional secondary battery; and

FIG. 6 is a sectional view of a cap assembly for a conventional secondary battery.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, the prismatic battery will be used as an example to describe a structure of the conventional secondary battery with reference to FIG. 5. The basic structure of the conventional prismatic secondary battery includes a prismatic can 1; an electrode assembly 9 formed in a jelly roll configuration by interposing separators 7 between anode plates 3 and cathode plates 5, on which an active material is deposited, the electrode assembly 9 being provided in the can 1; and a cap assembly 11 provided to an opening of the can 1 to seal the same, the cap assembly 11 being electrically connected to the electrode assembly 9.

Referring also to FIG. 6, the cap assembly 11 includes a cap plate 11 a integrally assembled to the can 1 to form a seal with the same; a tab welding plate 11 b for fixing an electrode tab 13 that is connected to one of the electrode plates of the electrode assembly 9 (e.g., one of the cathode plates 5); an insulating member 11 c provided as insulation between the cap plate 11 a and the tab welding plate 11 b; an electrode pin 11 d that passes through holes formed in the cap plate 11 a, the tab welding plate 11 b, and the insulating member 11 c to contact the tab welding plate 11 b for electrical connection to the same; and a gasket 11 e providing insulation between the electrode pin 11 d and the cap plate 11 a.

However, with the use of the cap plate 11 having the structure described above by the secondary battery, in the case where the gasket 11 e experiences problems such that it undergoes deformation, electrolyte within the can 1 easily leaks such that battery performance is reduced. This is a result of an area between the electrode pin 11 d and the gasket 11 e that is closely contacted, that is, a connecting area of a head portion 110 d and a column 112 d of the electrode pin 11 d being smooth and flat such that if the gasket 11 e is deformed, the electrolyte within the can 1 travels along the column 112 d of the electrode pin 11 d and easily exits the can 1 through the head portion 110 d.

Further, a bottom surface of the insulating member 11 c that sits on the tab welding plate 11 b is flat such that during assembly of the cap assembly 11, when calking of the electrode pin 11 d to the cap plate 11 a, the insulating member 11 c, and the tab welding plate 11 b is performed, the force used during calking is applied to all of the insulating member 11 c such that a significant reactive force is generated from the insulating member 11 c. This reactive force acts to deform the insulating member 11 c itself such that the seal formed at the bottom of the cap assembly 11 is broken or made less effective.

Finally, in the secondary battery having the cap assembly 11 as described above, it is necessary to provide a separate space for the placement of the electrode tab 13 between the tab welding plate 11 b and the electrode assembly 9. This interferes with attempts to maximize the volume of the electrode assembly 9 within the can 1, which, in turn, makes increasing battery capacity difficult.

FIG. 1 is a partial sectional view of a secondary battery according to an embodiment of the present invention. As an example, the secondary battery used for description is a lithium ion secondary battery that has a rectangular exterior.

The secondary battery includes an electrode assembly 22 provided within a rectangular can 20 and formed of anode plates, cathode plates, and separators. Also, a cap assembly 24 is connected to an opening 20 a of the can 20. The can 20 defines an exterior of the secondary battery. In addition to the electrode assembly 22, there is provided electrolyte within the can 20. The anode plates and cathode plates of the electrode assembly 22 are wound together with separators interposed therebetween to realize a jelly roll configuration.

Further, the cap assembly 24 is seated in the opening 20 a of the can 20 and is fixed thereto by welding or other means to seal the inner space within the can 20. The cap assembly 24 is to electrically connected to the electrode assembly 22. Describing the cap assembly 24 in more detail, a cap plate 24 a forms a base of the cap assembly 24 and is connected to the opening 20 a of the can 20. A cylindrical hole 240 a of a predetermined size is formed in substantially a center of the cap plate 24 a, and an electrolyte injection hole and a safety vent (both not shown) are formed to both sides of the hole 240 a.

A tab plate 24 b is mounted to an inner surface of the cap plate 24 a (a surface within the can 20). The tab plate 24 b is electrically connected to the electrode assembly 22. An insulating plate 24 c is interposed between the tab plate 24 b and cap plate 24 a, and insulates these elements from each other. Also, holes 240 b and 240 c that communicate with the hole 240 a of the cap plate 24 a are formed in the tab plate 24 b and the insulating plate 24 c, respectively. In the preferred embodiment of the present invention, a lead 26 extends from a cathode plate of the electrode assembly 22 to the tab plate 24 b, and a tab (not shown) extends from an anode plate of the electrode assembly 22 to the cap plate 24 a.

The cap plate 24 a, the tab plate 24 b, and the insulating plate 24 c are interconnected through the electrode pin 24 d that is inserted into the holes 240 a, 240 b, and 240 c of the cap plate 24 a, the tab plate 24 b, and the insulating plate 24 c, respectively. That is, after the electrode pin 24 d is inserted into the holes 240 a, 240 b, and 240 c, a connecting method such as calking is used to form the cap plate 24 a, the tab plate 24 b, and the insulating plate 24 c into an integral unit with the electrode pin 24 d. A head portion 242 d of the electrode pin 24 d is provided to a side of the cap plate 24 a opposite that contacting the insulating plate 24 c (i.e., to the outside of the can 20). The electrode pin 24 d is shown in FIG. 1 in a state mounted to form the cap assembly 24, that is, after it has undergone calking and with a column 240 d thereof deformed in a mounting state. In FIG. 2, the electrode pin 24 d is shown before it is placed within into the holes 240 a, 240 b, and 240 c such that its column 240 d is not yet deformed. An insulating gasket 24 e is interposed between the electrode pin 24 d and the cap plate 24 a. A hole 240 e is also formed in the insulating gasket 24 e into which the electrode pin 24 d is inserted.

With respect to the formation of the head portion 242 d of the electrode pin 24 d, an area of the head portion 242 d contacting the insulating gasket 24 e (a lower end of the head portion 242 d when viewing FIG. 1) is formed in a multiple stage configuration. The head portion 242 d of the electrode pin 24 d is formed in this manner so that in the case where electrolyte leaks from within the can 20 during operation of the secondary battery, the path through which leakage occurs is lengthened to thereby increase the time required for the leakage process (as seen for example by direction arrows in FIG. 3).

The structure of the electrode pin 24 d will be described in more detail. First, the head portion 242 d of the electrode pin 24 d is formed in a multistage configuration as described above. That is, a center portion of the head portion 242 d is formed protruding from the remainder of the head portion 242 d. As shown in FIG. 2, the head portion 242 d of the electrode pin 24 d includes a first stage 244 d, which has a predetermined thickness d1, and a second stage 246 d, which is formed on a side of the first stage 244 d contacting insulating gasket 24 e and having a thickness d2 that is less than the thickness d1 of the first stage 244 d. The second stage 246 d is formed with an uneven outer surface. For example, the second stage 246 d may be formed with a thickness that increasingly expands in a direction away from a center of the second stage 246 d. However, the present invention is not limited to such a configuration and other shapes may be used for the second stage 246 d of the head portion 242 d.

In the secondary battery of the present invention structured as in the above, if some defects are present in the cap assembly 24, for example, if there are minute defects in the insulating gasket 24 e, leakage of the electrolyte within the can 20 may result. If this occurs, the path of electrolyte leakage is increased by the uneven surface of the second stage 246 d of the head portion 242 d of the electrode pin 24 d (as seen for example by the direction arrows in FIG. 3 showing leakage). In particular, when electrolyte that starts to leak from inside the can 20 travels along the column 240 d of the electrode pin 24 d and toward the head portion 242 d, the speed at which the electrolyte is traveling is reduced over the earlier art as a result of having to travel over the curved form of the second stage 246 d of the head portion 242 d. Therefore, the time required for electrolyte to leak outside of the can 20 increases considerably.

The head portion 242 d of the electrode pin 24 d that is formed in multiple stages not only delays the electrolyte leakage time, but the curved area of the head portion 242 d acts to provide a better seal with the insulating gasket 24 e so that leakage may be prevented.

Deformation of the insulating plate 24 c occurs during calking of the electrode pin 24 d. Electrolyte leakage that may be caused by this deformation is prevented by the formation of a seal-enhancing member 242 c (see FIG. 4). The seal enhancing member 242 c acts such that when the electrode pin 24 d is connected to the above plates through a calking process, a resulting connective force is not transmitted to the parts of the insulating plate 24 c (i.e., peripheries around the hole 240 c of the insulating plate 24 c), and instead is concentrated on the seal enhancing member 242 c itself.

In the preferred embodiment of the present invention, the seal enhancing member 242 c is realized through a hilly spot formation that protrudes from an inner surface of the insulating plate 24 c around a periphery of the hole 240 c of the insulating plate 24 c. During manufacture of the cap assembly 24, the seal enhancing member 242 c first contacts (before the inner surface of the insulating plate 24 c) an upper surface of the tab plate 24 b when the insulating plate 24 c is assembled to the tab plate 24 b. As a result, the force generated during calking of the electrode pin 24 d is concentrated on the seal-enhancing member 242 c.

By such operation of the seal-enhancing member 242 c, the insulating plate 24 c prevents deformation of other areas extending past the peripheries of the hole 240 c. This ensures a state of close contact between the cap plate 24 a and the tab plate 24 b to further prevent the leakage of electrolyte from the cap assembly 24.

It is preferable that the tab plate 24 b of the cap assembly 24 is made of a nickel alloy. Nickel alloy ensures that the tab plate 24 b has a high degree of hardness such that deformation of the tab plate 24 b is prevented when the electrode pin 24 d is calked (during manufacture of the cap assembly 24).

Further, formed in the tab plate 24 b that extends in a direction toward the electrode assembly 22 is a receiving area 242 b for holding the lead 26. The receiving area 242 b is a groove formed at a predetermined depth on one side of the tab plate 24 b. The lead 26 is provided in a bent configuration as shown in FIG. 1, with one end being welded in the receiving area 242 b.

With the lead 26 mounted in the receiving area 242 b to be connected to the tab plate 24 b, a separate space need not be provided as in the conventional secondary battery for the lead 26. The space needed inside the can 20 is therefore reduced. This allows the electrode assembly 22 to be enlarged by as much as the saved space such that battery capacity may be increased. In particular, it was determined that an increase of 2% in capacity (e.g., a capacity increase of 20 mAh (milli-ampere hour) for a battery of a 1000 mAh capacity) was realized with the use of the receiving area 242 b rather than the extra space for the lead in the conventional battery.

In addition, a stable mounting structure is realized with the above method of fixing the lead 26 within the receiving area 242 b. As a result, the possibility of the lead 26 becoming disconnected is reduced when the cap assembly 24 is mounted to the can 20. Also, the fixing of the lead 26 within the receiving area 242 b (by welding as described above) is easy.

In the secondary battery of the present invention described above, the quality of the seal made between the cap assembly and can is improved to better prevent the leakage of electrolyte. Also, in the case leakage does occur, the present invention is configured such that the leakage takes place more slowly to thereby prevent a reduction in the lifespan of the battery caused by electrolyte leakage.

Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims. 

1. A secondary battery, comprising: a can; an electrode assembly provided inside said can; and a cap assembly comprising: a cap plate configured to seal an opening of said can encasing the electrode assembly; a tab plate mounted to one side of said cap plate to electrically connect said electrode assembly; an insulating plate interposed between said cap plate and said tab plate; an insulating gasket lying upon said cap plate; and an electrode pin passing through said cap plate, said tab plate, and said insulating plate to interconnect said cap plate, said tab plate, and said insulating plate, said electrode pin comprising: a shaft extending along an axis from engagement with said tab plate and through said insulating plate, said cap plate and said insulating gasket, a head terminating the shaft and extending by a first radial distance radially from said axis to provide a periphery engaging the insulating gasket on an exterior side of the cap plate, and a shoulder interposed between said shaft and said head extending by a second and lesser radial distance radially from said axis to provide a peripheral surface engaging the insulating gasket, with axial thickness of said peripheral surface increasing toward said insulating gasket as a function of said radial distance from said axis.
 2. The secondary battery of claim 1, wherein said head and shoulder form multiple stages on said electrode pin and are realized with a center area of said head being formed protruding from a remainder of said head.
 3. The secondary battery of claim 2, wherein said multiple stage configuration of said head of said electrode pin includes a first stage including a predetermined thickness, and a second stage including a thickness being less than the thickness of said first stage.
 4. The secondary battery of claim 3, wherein a surface of said second stage is uneven.
 5. The secondary battery of claim 4, wherein the second stage is formed having a thickness increasingly expanding in a direction away from a center of the second stage.
 6. The secondary battery of claim 1, wherein said can is prismatic.
 7. The secondary battery of claim 1, wherein a recess is formed in a surface of said tab plate facing said electrode assembly, and a lead is bent and mounted in the recess in a state electrically connected to said electrode assembly.
 8. The secondary battery of claim 7, wherein the recess is formed as a groove in said tab plate.
 9. The secondary battery of claim 1, with said insulating plate providing a surface perforated by an aperture accommodating passage of said shaft of said electrode pin, said insulating plate protruding beyond said surface around a periphery of said aperture and forming a seal enhancing member.
 10. The secondary battery of claim 9, wherein said seal enhancing member is realized through a rim protruding from one surface of said insulating plate around the periphery of the hole of said insulating plate.
 11. The secondary battery of claim 9, wherein said can is prismatic.
 12. The secondary battery of claim 9, wherein a recess is formed in a surface of said tab plate facing the electrode assembly, and a lead is bent and mounted in the recess in a state electrically connected to said electrode assembly.
 13. The secondary battery of claim 12, wherein the recess is formed as a groove in said tab plate.
 14. The secondary battery of claim 1, with said tab plate being made of a nickel alloy.
 15. The secondary battery of claim 14, wherein the can is prismatic.
 16. The secondary battery of claim 14, comprising a recess formed in a surface of said tab plate facing said electrode assembly, and a lead directly mounted in the recess and electrically connected to said electrode assembly.
 17. The secondary battery of claim 14, comprising a recess formed as a groove in said tab plate, oriented to receive an electrical lead connected with the electrode assembly.
 18. The secondary battery of claim 1, further comprised of said head having a plurality of stages including at least a first and a second stage, said second stage being connected to said shaft, said second stage having a different form than said shaft and said second stage having a different form than said first stage.
 19. The secondary battery of claim 18, with said second stage including a greater perimeter than said shaft and said first stage having a greater perimeter than said second stage, with said second stage including a curved form and said cap plate, tab plate, and insulating plate forming an integral unit with said electrode pin, with said second stage being directly disposed on said first stage and said head protruding outside of said cap plate and said can.
 20. A secondary battery, comprising: a can including an interior space; an electrode assembly provided in the interior space of said can; and a cap assembly seated on an opening formed in said can to seal said can and electrically connected to said electrode assembly, with said cap assembly comprising: a cap plate connected to the opening to seal said can; a tab plate spaced-apart from said cap plate and connected to said electrode assembly; an insulating plate interposed between said cap plate and said tab plate; an electrode pin passing through said cap plate, said tab plate, and said insulating plate to interconnect said cap plate, said tab plate, and said insulating plate, said electrode pin comprising: a shaft extending along an axis from engagement with said tab plate and through said insulating plate, said cap plate and said insulating gasket, a head terminating the shaft and extending by a first radial distance radially from said axis to provide a periphery engaging the insulating gasket on an exterior side of the cap plate, and a shoulder interposed between said shaft and said head extending by a second and lesser radial distance radially from said axis to provide a peripheral surface engaging the insulating gasket, with axial thickness of said peripheral surface increasing as a function of said radial distance from said axis.
 21. A secondary battery, comprising: a can; an electrode assembly provided inside said can; and a cap assembly, said cap assembly comprising: a cap plate to seal said can; a tab plate spaced-apart from said cap plate bearing a recess oriented to receive an electrical lead connected with the electrode assembly; an insulating plate interposed between said cap plate and said tab plate, said insulating plate comprising a rim protruding from one surface of said insulating plate around the periphery of an aperture in said insulating plate to engage said tab plate; an insulating gasket extending through said cap plate and said aperture; an electrode pin passing through and interconnecting said insulating gasket, said cap plate, said insulating plate, and said tab plate, said electrode pin comprising: a shaft extending along an axis from engagement with said tab plate and through said insulating plate, said cap plate and said insulating gasket, a head terminating the shaft and extending by a first radial distance radially from said axis to provide a periphery engaging the insulating gasket on an exterior side of the cap plate, and a shoulder interposed between said shaft and said head extending by a second and lesser radial distance radially from said axis to provide a peripheral surface engaging the insulating gasket, with axial thickness of said peripheral surface increasing as a function of said radial distance from said axis.
 22. A secondary battery, comprising: a cap assembly comprising: a cap plate configured to seal an opening of a can encasing a core of a battery; a tab plate mounted to one side of said cap plate to electrically connect an electrode assembly for the core; an insulating plate interposed between said cap plate and said tab plate; an insulating gasket lying upon said cap plate; and an electrode pin passing along an axis through said cap plate, said tab plate, and said insulating plate to interconnect said cap plate, said tab plate, and said insulating plate, said electrode pin comprising: a shaft extending along said axis from engagement with said tab plate and through said insulating plate, said cap plate and said insulating gasket, a head terminating the shaft and extending by a first radial distance radially from said axis to provide a periphery engaging the insulating gasket on an exterior side of the cap plate, and a shoulder coaxially interposed between said shaft and said head extending by a second and lesser radial distance radially from said axis forming a concave peripheral surface engaging the insulating gasket. 